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Your roses have been planted, nurtured and have exploded into full bloom. Now what? Most reference books cover planting, pruning, and even pest control, quite thoroughly. These are certainly the most frequently asked questions about rose care. But what about midsummer maintenance? It's a topic commonly overlooked but very important for continuous bloom and plant vigor. Here are a few tips for keeping the bloom explosion going all summer.
Most modern roses, even some heirloom varieties, will bloom all summer if properly groomed. "Deadheading" refers to the process of removing old or spend flowers from the bush. Whether you've been cutting the flowers to enjoy indoors or have left them on the bush to beautify the garden, proper trimming ensures strong reblooming. By deadheading roses instead of allowing them to form seed hips, you're signalling the plant to produce more flowers. It's also a way to continually prune and shape the plant.
Rose leaves develop in sets of three, five, even seven or nine leaflets. Notice the five leaflet leaves; these are where you'll want to prune. Cut 1/4" above a five-leaflet leaf, leaving at least two sets of leaflets on the stem from which you're cutting. Pick a leaf that faces outward to cut above and make the cut at an angle sloping downward toward the center of the bush. Also, be sure to cut stems back to wood strong enough to support a new rose - at least pencil-thick is a good guide. If stems are too small they will either "go blind" (won't produce a bloom) or will be unable to support the bloom's weight.
While most rose gardeners fertilize in the spring when growth begins, midsummer feeding sometimes gets overlooked. Roses are heavy feeders - it takes a lot of energy to produce all those large, magnificent blooms! Many different fertilizers do the job - you can choose from granular, liquid, organic or slow-release. While each formula has its advantages, keep in mind that roses prefer a fairly balanced fertilizer where the N-P-K (nitrogen, phosphorus, potassium) ratios are fairly even (i.e. 15-15-15 or 5-10-5). High-nitrogen fertilizers without enough phosphorus and potassium, such as lawn fertilizers, will produce lush green foliage while sacrificing blooms.
You can combine deadheading and fertilizing, since they should both be done about every 4-6 weeks. Hybrid tea and floribunda roses produce new blooms 5-6 weeks after deadheading, while miniatures and shrubs will recycle in about 4-5 weeks.
pH measures the acidity (or alkalinity) of your soil. It's an important consideration because of its affect on fertilizer. If soil is overly acidic or alkaline, then nutrients might be "tied up" in the soil and won't be available to the plant, no matter how much fertilizer you apply. Roses prefer slightly acidic soils (pH of 6.5-7.0). Since some fertilizers can acidify the soil and since some areas have alkaline water, it's a good idea to check your soil pH and adjust accordingly by adding garden lime (dolomitic lime works well) if too acid, aluminum sulfate or acidifying fertilizer if too alkaline. Adding more organic matter (compost, peat moss, decomposed bark, etc.) to the soil also helps to stabilize the effects of low or high pH.
Roses like a good, deep soak to promote deep rooting and they will actually develop drought tolerance if established this way. Frequent light waterings promote shallow roots that will depend on frequent watering. Applying the water slowly with soaker hoses or drip irrigation allows the water to soak in rather than running off, keeps water off the foliage (wet leaves spread fungal diseases), and reduces the puddling which can cause clay soils to form a hard surface less permeable to water. Mulching helps by reducing evaporation, retaining moisture, and preventing the soil surface from caking. If you use overhead watering, do it in the morning so that the foliage will have plenty of time to dry off before nighttime. Roots need air as well as water, so don't keep the soil continually soaked. Allow the top inch to dry off before watering again.
Pests and Diseases
Early detection and prevention keep these problems under control. While good things come in threes, so do bad. Since aphids are mainly a spring pest, the "Big Three" summer pests are thrips, spider mites, and in the eastern and southern United States, Japanese Beetles.
Thrips mainly attack rose blooms, especially whites and yellows, and mites attack foliage, turning leaves a mottled brown and leaving their tell-tale fine webbing. If detected early, these pests can be controlled with one or two sprays of an organic or chemical remedy. An initial control for both mites and aphids is a wash with a jet of water from the garden hose. Depending on the severity and timing, Japanese beetles can be picked off, sprayed or trapped. If trapping, place traps away from your roses so they won't be attracted to them.
The "Big Three" of rose diseases are blackspot, powdery mildew and rust, all of which are types of fungus. Blackspot occurs during humid or rainy weather or where watering (especially overhead) is excessive. Powdery mildew prefers warm days and cool nights, crowded plantings or damp, shady areas. Rust develops on moist foliage, so areas with heavy dew or fog are prone to this disease. Proper rose culture, including plenty of sun, sufficient air circulation, proper watering and sanitation (disposing of old leaves and other debris) will minimize all three disease problems, but they may still occur. If detected early and treated with a fungicide (organic or chemical), none of these will spread out of control.
Whatever spray you use for pest or disease control, always be sure to follow the directions on the label! This applies to organics as well as chemical sprays. Even organics can be toxic if used incorrectly.
It's time to stop and smell the roses. With proper summer care, roses will be there for you to smell all season. And what a wonderful reward for the effort - a garden full of lush color, a welcome retreat from the "dog days" of summer.